KR100798590B1 - Process for photoresist regeneration and system thereof - Google Patents

Abstract

The present invention relates to a photoresist regeneration method and a system thereof. This concentrates and extracts the volatile washing solvent in the recovered photoresist solution at low temperature to obtain a solids content volume that is greater than the solids content volume of the fresh photoresist. The recovered photoresist is further filtered to remove particulates contained therein and photoresist dilution reagent is added to adjust its solids content and viscosity to bring the estimated film thickness closer to that of the new photoresist. The recycled photoresist obtained as above can be reused and has a lower volatility. This helps to improve the thickness of the photoresist in four corners when coating the substrate.

Photoresist

Description

Photoresist regeneration method and system therefor {PROCESS FOR PHOTORESIST REGENERATION AND SYSTEM THEREOF}

1 shows a flowchart of regeneration of a photoresist according to the present invention.

2 shows a schematic diagram of a photoresist regeneration system according to the present invention.

3A is a 3D graph showing coating uniformity of regenerated photoresist that has not undergone a concentration process.

3B is a 3D graph showing coating uniformity of regenerated photoresist that has undergone a concentration process.

The present invention provides a photoresist regeneration method and system for extracting various volatile washing solvents by concentration at low temperature for regeneration and reuse of photoresist.

In optoelectronic or semiconductor processes, photoresists are typically deposited on glass substrates by spin coating. In order to obtain a uniform coating, the photoresist is typically dispensed in excess. Generally, about one tenth of the dispensed photoresist is deposited on a glass substrate, while the remainder rotates or is discharged onto the inner wall of the collection tank. In the coating process, the machine will periodically clean the inner wall with a solvent to wipe off the photoresist on the wall and the cleaning solvent and photoresist will flow into the collection tank. The photoresist in the collection tank is diluted with a large amount of washing solvent contained in the collection tank.

The coating process produces dry and wet films depending on the film thickness of the coated photoresist. The thickness of the wet film varies with the kinetic viscosity of the photoresist (μ / ρ; μ is the viscosity of the photoresist and ρ is the density of the photoresist). The proportion of solvent also affects the thickness of the wet film. In baking the substrate after photoresist coating, the solids content of the photoresist affects the thickness of the dry film; Higher solids content will produce thicker films and lower solids content will produce thinner films.

In the case of directly reusing the recovered waste photoresist, its film thickness may be problematic because its solid content may be too low due to the content of the washing solvent, or may result in poor coating uniformity due to the inclusion of highly volatile solvents. will be. Therefore, the recovered photoresist must be concentrated and processed before reuse.

TW 389850 discloses a device for recovering photoresist released from a rotating coater, which collects a mixture of excess photoresist and washing solvent at predetermined intervals using a drive motor at an alternating speed in a set of rotating coaters. "Is disclosed. The patented technology merely provides a method of recovering the waste photoresist solution and does not initiate the reuse of the recycled waste photoresist sheet. JP Patent No. 11-133619 discloses a photoresist regeneration method for collecting a waste solution containing waste photoresist and EBR and measuring the solids content thereof; At this time, if the solid content is too high, the solvent is added to adjust the concentration; Conversely, excess solvent is evaporated. The photoresist is then filtered to remove particulates and contaminants. The patent only provides the concept of recovery of the photoresist and does not suggest specific control conditions for the control of the recovered photoresist.

Regarding photoresist regeneration and reuse, TW Patent 200535414 discloses a monitoring method, a regeneration method and a system for photoresist regeneration, wherein the waste photoresist is concentrated by concentrating a volatile washing solvent (ie acetone) under reduced pressure. Extracting from the solution or diluting the waste photoresist solution with a photoresist thinner to adjust its solids content and viscosity, and then the recovered photoresist is filtered to remove particulates to obtain a reusable photoresist. However, if the recovered photoresist contains a low volatility solvent such as propylene glycol methyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), or n-butyl acetate (N-BA) Solvents are not easily extracted by concentration under reduced pressure.

Therefore, there is a need to develop a photoresist regeneration method suitable for photoresists containing all kinds of washing solvents.

The solids content of the recovered photoresist is poor due to the content of the washing solvent or due to the content of volatile solvents (eg propylene glycol methyl ether, propylene glycol monomethyl ether acetate, or n-butyl acetate) that are difficult to extract. Will produce a coating layer with uniformity. Therefore, the recovered photoresist must be concentrated and processed before reuse. It is an object of the present invention to provide a method of regenerating a photoresist, which extracts the washing solvent in the waste photoresist by low temperature concentration. The concentrated photoresist has a low volatility, which effectively improves the thickness of the photoresist in four corners when coating the glass substrate.

It is another object of the present invention to provide a photoresist regeneration system which improves the concentration efficiency by using a low temperature concentration apparatus to extract the wash solvent in the recovered photoresist.

Still another object of the present invention is to provide a regenerated photoresist that can be used for photoresist coating in optoelectronic or semiconductor processes.

In order to achieve the above objects, the present invention provides a photoresist regeneration method comprising the following steps:

(a) extracting by washing at low temperature the washing solvent in the recovered photoresist solution until the solids content of the recovered photoresist is higher than the solids content of the fresh photoresist;

(b) removing particulates in the concentrated photoresist by filtration;

(c) adding a solvent to adjust the solids content and viscosity of the recovered photoresist;

(d) monitoring the solids content (C ₀ ) and viscosity (μ ₀ ) of the adjusted photoresist; And

(c) obtaining a target film thickness (H _f ) by adjusting the solids content and viscosity of the recovered photoresist under a fixed rotational speed.

The present invention comprises the steps of concentrating the recovered photoresist at low temperature to make its solids content higher than for a new photoresist; And adjusting the solids content and viscosity of the concentrated recovered photoresist to be close to the case of a new photoresist, wherein the method provides a solvent for the recovered photoresist. Extraction by low-temperature condensation increases the solids content in the photoresist.

Preferably, the solids content of the concentrated recovered photoresist is 3-8% higher than that of the new photoresist, and more preferably 5% higher than the solids content of the new photoresist.

In the present invention, the term " recovered photoresist " refers to waste photoresist in a collection tank that has been used but not processed by the photoresist regeneration process, and can be viewed as a raw material for the photoresist regeneration process. have. The recovered photoresist may have been diluted by a mixture of washing solvents or concentrated as a result of air intake which changes its solids content and viscosity. The term "regenerated photoresist" refers to waste photoresist that has passed through processing steps of solids content control, viscosity control and impurity removal. After the treatment step, the regenerated photoresist meets the usage specifications for solids content and viscosity and can be reused in the process. The term "target thickness" refers to the expected film thickness of regenerated photoresist produced under a fixed rotational speed.

The present invention provides a low temperature concentrating device; Solvent supply apparatus; A monitor unit comprising a content tester and a viscometer; And a filtration unit comprising at least one filter having a pore size in the range of 1.0 to 0.1 μm.

The present invention provides a regenerated photoresist made from the photoresist regeneration method according to the present invention, which can be used in optoelectronic or semiconductor processes.

The present invention extracts the wash solvent in the recovered photoresist by low temperature concentration, and then adds the solvent to adjust the viscosity and solids content of the recovered photoresist to obtain a regenerated photoresist having a target film thickness do. After coating, development and etching tests, the performance of the regenerated photoresist obtained according to the present invention is close to the specification of the new photoresist and improves the thickness problem in the four corners of the prior art. appear. The test results indicate that the method disclosed in the present invention can effectively recycle the photoresist and achieve the purpose of cost reduction and resource recovery by monitoring the properties of the regenerated photoresist.

The present invention extracts the washing solvent in the recovered photoresist solution by the low temperature concentration principle. Since the solvents have different saturated vapor pressures and volatility, the nitrogen is supplied to the chamber and the chamber is kept at low temperature while the recovered photoresist solution is concentrated so that the properties of the photoresist are not affected or the photoresist reacts. Do not suffer. Subsequently, the recovered photoresist is filtered to remove fine particles contained therein, and a solvent is added to adjust the solvent ratio thereof. A quantitative equation showing the relationship between viscosity, solids content and film thickness is then used to determine the solids content and viscosity of the regenerated photoresist and obtain a photoresist with the desired target thickness.

In the photoresist coating method there are dry films and wet films. The thickness of the wet film varies with the kinematic viscosity of the photoresist (μ / ρ; μ is the viscosity of the photoresist and ρ is the density of the photoresist). The proportion of solvent also affects the thickness of the wet film. In the firing of the substrate after photoresist coating, the solids content of the photoresist also affects its film thickness; Higher solids content will produce thicker films and lower solids content will produce thinner films. Based on the above description, under various assumptions, the relationship between dry film thickness and wet film thickness can be expressed as follows (Meyerhofer, D., “Characteristics of Resist Films Generated by Rotation,” J. Appl. Phys., 49 (7), p3993-3997, 1978):

^{_{H f = (3/2) 1/3 k}} 1/3 C 0 (1-C 0) -1/3 ρ -1/3 μ 0 1/3 Ω -1/2

Where

H _f is the dry film thickness (constant),

k is the constant of the relevant solvent,

C ₀ is the initial solids content,

ρ is the density,

μ ₀ is the initial viscosity of the solution,

Ω is the rotational speed.

Experimental results show that Equation 2 cannot demonstrate the exact relationship of dry film thickness, solids content and viscosity. In addition, the photoresist density and the dispensing rotation speed of the photoresist are typically fixed. Under the assumption that the photoresist density and rotational speed are fixed values, the rotational speed and density factor are bounded by constants in Equation 2, and a simplified equation (1) representing the relationship between film thickness, solid content and viscosity is obtained from the reproduced photoresist. It is proposed as a quantification equation for quality control.

H _f = k ₀ C ₀ ^α μ ₀ ^β

Where

k ₀ , α, β are constants,

C ₀ is the solids content of the solution,

μ ₀ is the viscosity of the solution.

The values of k ₀ , α and β can be obtained from the experiments illustrated in the examples below. The present invention controls the quality of the regenerated photoresist by monitoring the weight and viscosity of its solids content.

1 and 2 illustrate the application of the photoresist regeneration method and the monitoring method disclosed in the present invention of the photoresist regeneration system in detail. 1 is a flowchart of a photoresist regeneration method according to the present invention. 2 is a schematic diagram of the photoresist regeneration system 10. The photoresist regeneration method is performed in a photoresist regeneration system 10 comprising a low temperature concentration device 1, a monitor unit 2, a filtration unit 3, and a solvent supply device 4, wherein the low temperature concentration device ( 1) a compressor 11, a cooling device 12, a radiator 13, a thermostat 14 and a filter-dryer 15; The monitor unit (2) comprises a content tester (21) and a viscometer (22); The filtration unit 3 comprises one or more filters having a pore size in the range of 1.0 to 0.1 μm. The solvent supply device 4 is for adding a solvent to adjust the solids content and viscosity of the regenerated photoresist to be close to the values of the new photoresist.

The low temperature concentration apparatus used by the present invention performs concentration of the photoresist by drying. Since the photoresist is heat sensitive, the concentration process must be carried out under low temperature using a compressor and thermostat. First, the temperature of saturated air circulating in the chamber is lowered below the dew point using the cooling device 12, at which time the solvent vapor in the air will be concentrated. The air then passes through filter-dryer 15 to dry air. Since the content of solvent vapor in the dry air is minimal, when the dry air passes through a photoresist containing a highly volatile solvent, the vapor pressure difference between the air and the photoresist will cause the mass transfer of the solvent to reach equilibrium. .

Again, because the photoresist is photosensitive, the low temperature concentration process must be performed in a dark, closed space. In addition, the low temperature concentrating device should be designed in such a way that it increases the contact area between the photoresist and the dried air so that the concentration efficiency is improved. The photoresist regeneration process according to the present invention is as shown in FIG. 1; First, the waste photoresist from the optoelectronic or semiconductor process is examined to determine whether it is suitable for the regeneration process and discard if not. Acceptable waste photoresist is placed in a cold concentrator 1 for extraction of excess wash solvent to increase the solids content of the photoresist. The operating pressure of the low temperature concentration device is atmospheric pressure, and the temperature thereof is adjusted to 5 to 35 ° C, preferably 25 ° C. In the concentration process, the solids content and viscosity of the photoresist are monitored using the monitor unit 2. The concentration process is stopped when the solids content of the recovered photoresist reaches a 3-8% higher, preferably 5% higher, point than the new photoresist. The concentrated recovered photoresist is passed through a 0.1-1.0 μm membrane filter, preferably a 0.2 μm membrane filter to remove particulates therefrom. The photoresist diluent is then added using the solvent supply device 4. The diluent for adjusting the solids content and viscosity of the waste photoresist is preferably propylene glycol monomethyl ether (PGME) or propylene glycol monomethyl ether acetate (PGMEA) or mixtures thereof. The method for measuring the solids content of the photoresist recovered according to the present invention includes, but is not limited to, measuring the weight of the photoresist using a scale after firing. The solids content of the photoresist can also be measured using a spectrophotometer.

In the low temperature concentration and solvent addition process, the solids content and viscosity of the waste photoresist solution are monitored in the monitor unit 2 using the content tester 21 and the viscometer 22 respectively. The addition of the solvent is stopped when the solids content and viscosity of the recovered photoresist reach the values obtained through Equation 1 above. Finally, a waste photoresist having a controlled solids content is passed through a filtering device 3 'to remove particulates in the solution; The filtration device 3 'comprises a 0.1 to 1.0 μm membrane filter, preferably a 0.2 μm filter. The regenerated photoresist can be reused.

The invention is further illustrated in the examples, but the descriptions shown in these examples should not be construed as limitations on the practical application of the invention.

Example

Experimental apparatus

The experimental set up of this example includes the following:

Cold concentrators include compressors, chillers, radiators, thermostats and filter-dryers.

Monitor unit: includes content tester and ultrasonic viscometer.

Filtration unit: membrane filter with pore size of 0.8 μm and 0.2 μm.

Operating conditions for concentration: air temperature of 20-30 ° C.

Photoresist treatment temperature: 23 ° C.

Recovered Photoresist  Property measurement

Different coating processes may be used to dilute the waste photoresist with the amount of solvent used or to concentrate as a result of solvent extraction. Table 1 compares the physical properties of the new photoresist with the properties of the unconcentrated (diluted) recovered photoresist and the properties of the concentrated recovered photoresist as a reference for the photoresist regeneration method. As shown, the solids content and viscosity of the recovered photoresist without addition of the concentration are smaller than for the new photoresist, whereas the photoresist recovered after the concentration is greater than for the new photoresist.

Comparison of Properties between New Photoresist and Recovered Photoresist Solid content (%) Viscosity (cp) New photoresist 27.1 18.1 Recovered photoresist (not concentrated) 27.4 22.7 Recovered Photoresist (Concentrated) 30.6 38

The examples also test the volatilities of fresh photoresist, recovered photoresist that had not been subjected to concentration treatment, and concentrated recovered photoresist. The results shown in Table 2 indicate that because some highly volatile wash solvents were removed in the low temperature concentration process, the recovered recovered photoresist exhibited lower volatility than the recovered photoresist without addition of concentration. This will help to improve the photoresist thickness in four corners when coating onto the substrate.

Comparison of Volatilities of Photoresists New photoresist Recovered non-condensed photoresist Concentrated recovered photoresist Volatility (for EA) 0.061 0.178 0.113

Recycled Photoresist  Quality measurement

In this example, concentrated and unconcentrated recycled photoresists are subjected to optoelectronic or semiconductor processes to check their properties, followed by exposure and development to test their suitability in optoelectronic or semiconductor processes. The results are shown in Table 3.

Process conditions Film thickness tolerance standard: 15000 ± 500Å Uniformity Tolerance: 3% Remarks Regenerated photoresist without undergoing enrichment 15097 3.38% Dense in four corners (FIG. 3A) Regenerated Photoresist Under Concentration 15172 2.42% Improved thickness at four corners (FIG. 3B)

The results show that the film thickness of the regenerated photoresist that has not undergone concentration matches the acceptance criteria, but its uniformity is not, and the film tends to be too dense in four corners as shown in FIG. 3A. On the other hand, the film thickness and uniformity of the coating layer using regenerated photoresist treated according to the method disclosed in the present invention meet the acceptance criteria of optoelectronic or semiconductor process. More importantly, the regenerated photoresist according to the invention improves the thickness in four corners as shown in FIG. 3B, and its performance after exposure and development also meets the process requirements.

The present invention provides a photoresist regeneration method suitable for photoresists containing all kinds of cleaning solvents.

Preferred embodiments of the invention are disclosed in the examples. However, these examples should not be construed as limitations on the practically applicable scope of the present invention, and all changes and modifications are themselves departed from the spirit of the present invention and the appended claims, including other embodiments. It will fall within the protected scope and claims of the present invention without.

Claims (21)

(a) extracting the solvent in the recovered photoresist solution by cold concentration at atmospheric pressure until the solids content of the recovered photoresist is higher than the solids content of the new photoresist; (b) filtration to remove particulates in the cold concentrated and recovered photoresist; (c) adding a solvent to the recovered photoresist to adjust its solids content and viscosity; (d) monitoring the solids content (C ₀ ) and viscosity (μ ₀ ) of the recovered photoresist after said adjustment; And (e) obtaining a target thickness (H _f ) by adjusting the solids content and viscosity of the recovered photoresist under a fixed rotational speed Including but not limited to: Where the low temperature concentration of step (a) is stopped when the solids content of recovered photoresist is 3-8% higher than for the new photoresist, Regeneration method of photoresist. delete The method of claim 1, The low temperature concentration of step (a) is stopped when the solids content of the recovered photoresist is 5% higher than for the new photoresist. The method of claim 1, The operating temperature in step (a) of low temperature concentration is 5 to 35 ° C. The method of claim 4, wherein The operating temperature in step (a) of low temperature concentration is 25 ° C. The method of claim 1, The solvent of step (c) is a photoresist diluent. The method of claim 6, The photoresist diluent is propylene glycol monomethyl ether (PGME) or propylene glycol monomethyl ether acetate (PGMEA) or mixtures thereof. delete The method of claim 1, And wherein step (e) may further comprise a filtration unit for filtering the fines in the regenerated photoresist. The method of claim 1, Wherein the filtration of step (b) is suitable for passing the recovered photoresist through a filtration unit comprising at least one membrane filter having a pore size of 0.1 to 1.0 μm. The method of claim 10, The pore size of the membrane filter in step (b) is 0.2 μm. The method of claim 9, A filtration step is added following step (e), in which step the recovered photoresist is passed through a filtration unit comprising at least one membrane filter having a pore size of 0.1 to 1.0 μm. The method of claim 12, The pore size of the membrane filter is 0.2 μm. The method of claim 1, The recovered photoresist comprises a waste photoresist solution from an optoelectronic or semiconductor process. Atmospheric and cold concentrators; Solvent supply apparatus; A monitor unit comprising a content tester and a viscometer; And Filtration unit comprising one or more filters having a pore size in the range of 1.0 to 0.1 μm Photoresist regeneration system comprising a. The method of claim 15, A photoresist regeneration system wherein atmospheric and low temperature devices comprise a compressor, a cooling device, a radiator, a thermostat and a filter-dryer. The method of claim 15, A photoresist regeneration system wherein the low temperature concentrator has an operating temperature range of 5 to 35 ° C. A regenerated photoresist produced by the method according to claim 1. The recovered photoresist solution is treated by cold concentration to make its solids content higher than that of the new photoresist; A photoresist regeneration method comprising the steps of adjusting the solids content and viscosity of the concentrated recovered photoresist to be close to the case of a new photoresist, The concentration is performed at low temperature and atmospheric pressure to extract the solvent in the solution to increase the solids content of the recovered photoresist solution. The method of claim 19, Wherein the solids content of the concentrated recovered photoresist is 3-8% higher than for the new photoresist. The method of claim 20, 5% higher solids content of the concentrated recovered recovered photoresist.

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